Forging method



April 23, 1968 J. E. CARDILLO 3,378,903

FORGING METHOD Filed Oct. 25, 1965 u M a /4 f IN VE N TOR.

Jrry 6 474 22 0 BY United States Patent 3,378,303 FORGING METHOD Jerry E. Cardillo, Dearborn, Mich., assignor to Federal- Mogul Corporation, Detroit, Mich., a corporation of Michigan Filed Oct. 23, 1965, Ser. No. 503,400 23 Claims. (Cl. 29148.4)

ABSTRACT OF THE DISCLOSURE A method for forming ferrous bearing races at an inter mediate temperature between normal hot forging and cold forming temperatures.

The present invention relates to a method for forming parts at an intermediate temperature between normal hot forging and cold forming temperatures and to forming such parts from solid stock such as bar or wire and more specifically to methods of making bearing races. While scaling or oxidation of ferrous material will occur slowly at normal ambient temperatures, the rate of scaling increases With temperature.

In hot forging parts from steel the material is initially heated to around 2000 F. and higher. Thus at hot forging temperatures a substantial scale and a significant amount of decarburization will occur. Since the scale and the decarburized surfaces must be removed, there is by nature of this process a certain amount of material wasted not to mention the cost of the scale removal operation. Parts can be made without scale, by cold forming; however, the material at normal ambient temperatures has higher strength characteristics and hence can be shaped only with substantially higher forces. Frequently this would necessitate more cold forming stages whereby the material can be formed to a desired shape gradually. In addition if the material is worked to any considerable extent over a series of operations then cold working can increase the strength of the part whereby the part must be annealed in between successive cold forming operations.

In the present invention the parts are formed while the material is at an intermediate temperature high enough to reduce the strength of the material to facilitate forming and yet below the hot forging temperature at which scaling and decarburization occurs at a more rapid rate. It is an object of the present invention to provide a novel process for forming parts at a temperature below the normal hot forging temperature at which the strength of the material of the parts is substantially reduced while the formation of scale and the occurrence of decarburization is precluded to allow the manufacture of close tolerance forgings.

In the present invention a lubricant is utilized which will not vaporize at the intermediate temperature or at least will be on the part during the forming operation; the lubricant functions both to minimize scaling and decarburization and also to reduce the forces necessary to form the parts. By using the method of the present invention bar or wire stock can be utilized with a minimum amount of waste thereby providing for low material cost per part. Therefore it is an object of the present invention to provide a novel method for forming parts at an intermediate temperature in which bar or wire stock can be utilized and in which a lubricant is utilized to minimize scaling and decarburization while decreasing friction.

The extent of scaling is based upon a temperature-time relationship. While scaling does occur more rapidly at higher than at lower temperatures, the extent of scaling can be minimized at higher temperatures by minimizing the time the material is maintained at that temperature. Therefore it is another object of the present invention to provide a novel method for forming parts at high temperatures with a minimum amount of scale.

The present invention is specifically contemplated for use in the manufacture of annular parts such as hearing parts. Therefore it is an object of the present invention to provide a new and improved method. for manufacturing annular parts. It is a further object of the present invention to provide a new and improved method of manufacturing bearing races from bar or wire stock.

As a part of the present invention it is contemplated that more than one bearing race can be forged together as an integral forging. In this way inner and outer races could be forged together. However, it is also contemplated to conserve material to make bearing races together which are not associated. Hence a pair of inner or a pair of outer races could be forged together or an outer race for one bearing and an inner race for another bearing could be forged together either to provide the most advantageous use of material or to facilitate the manufacture of certain parts which may be required in greater or lesser quantities than others. Therefore it is another object of the present invention to provide a novel method "for manufacturing bearing races in which two or more races are forged together with the combination of races selected to minimize waste and/or to facilitate the manufacture of races which may be required in greater or lesser quantities.

The present invention also contemplates the integral forging of at least two races. By slightly axially separating the races they can be machined together hence reducing the number of handling steps, reducing the amount of time required to machine a given number of races and hence resulting in a cost saving. Therefore it is still another object of the present invention to provide a method for forging a plurality of bearing races as an integral member and machining the races together while still integral.

The subject invention is described and shown in conjunction with the manufacture of bearing races; it should be understood that while some of the features of the present invention may have particular utility in the manufacture of bearing races the scope of the present invention is not necessarily limited thereto.

Other objects, features, and advantages of the present invention will become apparent from the subsequent description and the appended claims, taken in conjunction with the accompanying drawings, in which:

FIGURE 1 depicts the solid wire or bar stock from which the parts can be made by means of the present inventlon;

FIGURE 2 depicts a slug which has been sheared off to a preselected size from the wire or bar stock of FIG- URE 1:

FIGURE 3 depicts the shape of the slug of FIG- URE 2 after it has been sized or formed into a workpiece;

FIGURE 3A depicts the shape of a different shaped workpiece which has been sheared from bar stock and which in a modified form of the process can be used in place of the workpiece shown in FIGURE 3;

FIGURE 4 represents in block form two steps which are performed upon the workpieces of FIGURES 3 and and 3A;

FIGURE 5 depicts the workpieces of FIGURES 3 and 3A formed into a cup-shaped part after heating step of FIGURE 4;

FIGURE 6 depicts the cup-shaped part of FIGURE 5 after having been machined to define an inner and outer bearing race;

FIGURE 7 is a sectional view of the inner and outer races of FIGURE 6 after having been separated; and

FIGURE 8 depicts the inner and outer races in a bearing assembly.

Looking now to the drawings, in FIGURE 1 the bar or wire stock from which the articles are made by the process or method of the subject invention is shown to be of a solid cylindrical form and is generally indicated by the numeral 10. First a preselected volume of material is sheared to form a slug 12 as shown in FIGURE 2. Next the slug 12 is sized by cold forming to fit the subsequent die and as shown in FIGURE 3 is formed into a solid cylindrically shaped workpiece generally indicated by the numeral 14. The workpiece 14 is then coated in a step indicated by the block designated with the numeral 16. The coating is provided to prevent oxidation or scaling and decarburization of the material of workpiece 14 which would occur at an accelerated rate at the high temperature subsequently involved; it is also desirable that this coating act as a lubricant in order to reduce the forces required to deform the workpiece 14. Since the slug is to be heated to a temperature at which the strength of the material is substantially reduced, the coatings selected are those which will not vaporize at this temperature or at least will vaporize slowly enough so that after heating, subsequent operations can be made with the coating still adhering to the surface of the workpiece 14. In one form of the invention the workpiece 14 being made of steel is first coated with manganese phosphate which acts as a carrier for the application of a lubricant which is tungsten disulphide. After the coating step, the workpiece 14 is then heated by induction or other suitable apparatus and this stage is generally indicated by the block designated by the numeral 18. In this step the workpiece 14 is heated to a high temperature which in the preferred form is below the normal hot forging temperature of the material and yet is substantially above the ambient temperature and at a level at which the strength of the material is substantially reduced. In the case of steel, temperatures in the range of between l300 and 1600 F. are preferred.

For case and through hardening steels used in the manufacture of bearing rings, etc., 1300 is the preferred temperature since it is still below the hot forging temperature at which scaling and decarburization are aggravated and yet provides for a substantial reduction in the strength of the material of the workpiece 14. To obtain an appreciable reduction in the strength of steel the minimum temperature contemplated is approximately 1000" F. The heating of the workpiece 14 to the desired temperature is done as rapidly as possible; by doing this the material will be at elevated temperatures for only a short time and hence, even without the application of a protective coating, scaling will be kept to a minimum. The combination, of course, of the use of a protective coating plus rapid heating provides the best results with the least amount of scale and decarburization and with the least amount of resultant frictional force.

The workpiece 14 while in the heated condition is placed in a female die 20 which defines a pair of circular coaxially located cavity portions 22 and 24, the portion 22 being of a smaller diameter than the portion 24. A knock-out punch 26 is located at the bottom of the portion 22. The workpiece 14 is formed with a recess which is of a size to receive the tip 27 of the knock-out 26 whereby the workpiece 14 is piloted in the cavity. With the workpiece thus located in the cavity a punch 28 having a preselected shape is caused to engage the workpiece 14 while at the elevated temperature whereby the cup-shaped part 30 is formed in a single strike.

The part 30 as for-med comprises a pair of generally annular ring portions 32 and 34 which correspond in outside diameter to the diameters of the cavity portions 22 and 24, respectively. The portions 32 and 34 are axially separated from each other and joined by a web 36. Offset from the bottom end of the smaller ring portion 32 is formed a fiat web 38. Note that the tip 27 extends partly 4 within the die cavity thus resulting in a flow of material both forward and reverse to fill the cavity. By so moving the material good flow is obtained and folds are eliminated. Thus by offsetting the web 38 good flow characteristics are obtained; by locating the web 38 offset from the bottom end the minimum thickness of the web 38 can be reduced from that minimum thickness obtainable if the web were located at the very bottom. In order to maintain good die life and to preclude the attainment of excessive loads on the dies, it has been found that the web 38 should be limited in its minimum thickness. For example, for a part such as 30 made of a bearing steel and having a diameter of 1% for the small diameter portion 22 the web 38 should have an average minimum thickness of approximately A1". Even at the elevated temperatures of the workpiece 14, attempts to reduce the metal in the web 38 to less than the average A1" thickness results in excessively high press loads. This average thickness will vary with different material and with different sized parts. It would be impossible to set forth the minimum thickness for all combinations of materials and sizes; it is sufficient that this limitation has been recognized and pointed out whereby now one skilled in the art could determine the minimum thickness for different combinations. It is also significant that the volume of material provided in workpieces 14 or 14a exceed by no more than ten percent the volume of the cavity defined by the die. If the volume exceeds ten percent the die loads increase to excessive levels. Thus the volume of the work pieces 14 and 14a should be controlled.

Note that the cup-shaped part 36 is obtained in one strike of the punch 28 from the workpiece 14. Under cold heading practices it would require several such strikes plus annealing and coating operations before a cup-shaped part such as the part 30 could be obtained from a workpiece such as workpiece 14. With the present invention even with larger or different parts in which more than one strike would be required the material could remain generally at the intermediate temperature for a time sufficient to permit additional strikes without reheating; of course, no intermediate annealing operation would be required. The number of strikes at the intermediate temperature still would be less than that required by cold forging and no intermediate anneal steps, as required by cold working would be necessary. Such a shape (as part 30), however, might be obtained in one blow by means of conventional hot forging, i.e. heating the material up to approximately 2000 F.; however, in conventional hot forging processes scaling forms to a substantial degree and hence a greater amount of material would have to be used to dimensionally end up with the same sized part since the scale would have to be removed.

If necessary or desirable the heating can take place prior to forming the workpiece 14; no reheating would be required, since the next strike (shown in FIGURE 5) could still be made prior to any substantial drop in material temperature. Also, rather than preforming a workpiece 14, a workpiece 14a (see FIGURE 3A) could b used. W'orkpiece 14a can be sheared from bar stock having a diameter substantially equal to the diameter of the small diameter cavity portion 22. The workpiece 14a will then be automatically piloted in the die; note that no sizing operation is required and workpiece 14a is used in the form as it is sheared from the bar stock.

With the two annular portions 32 and 34 connected together, the piece 30 can be machined together and assuming now that the ring portion 32 is to be the inner race of a ball bearing and the ring portion 34 is to be the outer race of the ball bearing, then the cup-shaped part 30 will be machined to a shape as shown in FIGURE 6. Note that the web 38 has been removed. Looking at FIGURE 6, portions similar to like portions of the cupshaped part 30 in FIGURE 5 have been given the same numerical designation with the addition of the letter subscript a. Thus the machined cup-shaped part 30a then will have its large diameter ring portion 34a with an inner raceway 40 machined therein and the small diameter ring portion 32a will have a raceway 42 formed on its outer surface. At the completion of this machining operation, the portions 32a and 34a can be separated by cutting away the connecting web portion 36a. Upon removal of the web 36a, a large diameter ring portion 34a defines an outer race member and the small diameter ring portion 32a defines an inner race member (see FIGURE 7) which can then be assembled with a plurality of balls indicated by the numeral 44 to form thereby a ball hearing assembly 46.

Note that while the specific embodiment shown is for the manufacture of ball bearing races, it should be understood that the present invention is equally applicable to the manufacture of other type bearing races including straight, tapered roller bearings and any type of annular rolling element type bearings.

Note then in this process that the inner and outer races can be machined separately or together. At the same time because of the close tolerances obtained by this process, the rings 32a and 34a need be machined only selectively, i.e., as to form raceways, chamfers, etc. For some bearing constructions the machining of raceways can be eliminated. The parts are now ready for hardening and grinding before assembly as shown in FIGURE 8. It can be appreciated that instead of forming inner and outer bearing races for the same bearing assembly, inner and outer races for different bearing assemblies can be simultaneously formed together and machined dually. Likewise, two outer or two inner races for different bearing assemblies could be formed together and machined dually.

Looking back to FIGURE 5, note that the ring portions 32 and 34 are axially offset from each other by means of the web 36. By providing such an offset structure, it has been found that the simple workpieces 14 and 14a can be utilized whereby the cup-shaped member 30 can be formed in one step or for large sizes in a minimum number of steps (less than that required by cold forming). In such an offset structure good flow characteristics are obtained and the part can be formed without folds or cracks. In addition, by so offsetting the portions 32 and 34, the dual machining of the two portions can be facilitated. If the two portions were nested it can be appreciated that dual machining would be impossible. However by nesting the parts the loss of material in web 36 would be eliminated; therefore, in some applications a nested forging would be desirable.

As previously noted, by first applying a protective coating prior to heating the workpiece 14 up to the forming temperature, scaling and decarburization will be prevented. Scaling and decarburization will occur, of course, with a steel part at substantially any temperature, with the rate of scaling and decarburization, however, generally increasing with an increase in temperature. Hence the selection of the coating will in part, at least, depend upon the temperature to which the part is heated and upon its cooling time. In the present invention it is contemplated that heating will be done by induction or other rapid means and with the forming being performed quick- 1y thereafter such that the part will be at the high temperature for only a short period. Thus the coating is selected to be such that it will not completely vaporize during the time interval between heating and forming after coating. Alternatively, the heating of the workpieces can be done in a controlled atmosphere in which scaling and decarburization will not occur. It is also desirable that some lubrication be provided between the die and the workpiece 14. Thus a coating which has lubricity characteristics as well as one which prevents scaling can be selected. The manganese phosphate tungsten disulphide coating previously discussed will serve the dual coating-lubricating function. Note that in lieu of applying a lubricant to the workpiece 14, a lubricant can be applied to the components of the die which contact the workpiece 14.

In working with steel, it is significant that some steels, i.e., high carbon, upon once being heated to the critical temperature, will harden upon cooling in air. When such materials are thus hardened, it is necessary to then perform a spheroidizing anneal operation to facilitate subsequent machining. The temperature at which this will occur for that material is normally referred to as the critical temperature. In the present invention, in order to avoid the necessity for a subsequent annealing operation, the part is heated to a temperature below the critical temperature of the material.

While it will be apparent that the preferred embodiments of the invention disclosed are well calculated to fulfill the objects above stated, it will be appreciated that the invention is susceptible to modification, variation and change without departing from the proper scope or fair meaning of the subjoined claims.

What is claimed is:

1. The method of forming bearing races from a ferrous material by deforming a workpiece comprising the steps of: heating the workpiece to a preselected temperature at which the strength of the material of the workpiece is substantially reduced from its strength at ambient temperature but below the critical temperature of the material at which air hardening occurs, deforming the workpiece while at said preselected temperature to form an intermediate part for making bearing races, and maintaining a protective coating on said workpiece while at said preselected temperature and during said deforming to prevent scaling and decarburization whereby said intermediate part is a close tolerance part requiring minimum machining.

2. The method of forming bearing races by deforming a workpiece made of a bearing type steel comprising the steps of: heating the workpiece to a preselected temperature, deforming the workpiece while at a temperature of approximately 1300" F. to form an intermediate part for forming bearing races, and maintaining a protective coating on said workpiece while at said preselected temperature and during said deforming to prevent scaling and decarburization whereby said intermediate part is a close tolerance part requiring minimum machining.

3. The method of forming a pair of bearing races from a ferrous material by deforming a slug comprising the steps of: deforming the slug to form a sized workpiece having a generally cylindrical shape, 'having the workpiece at a preselected temperature at least as high as around 1000 F. but below the critical temperature of the material at which air hardening occurs, locating the workpiece in a die having a pair of axially separated cavity portions, deforming the workpiece while at said preselected temperature in a single blow into an annular part having a pair of at least partially axially separated ring portions connected together by a web with the ring portions defining the pair of bearing races and maintaining a protective coating on said workpiece while at said preselected temperature and during said deforming step to prevent scaling and decarburization whereby said annular part is formed to close tolerances requiring minimum machining.

4. The method of forming a pair of bearing races from a ferrous material by deforming a slug comprising the steps of: deforming the slug to form a sized workpiece having a cylindrical shape, having the workpiece at a preselected temperature at least as high as around 1000 F. but below the critical temperature of the material at which air hardening occurs, locating the workpiece in a die having a pair of axially separated cavity portions, deforming the workpiece while at said preselected temperature in a single blow into an annular part having a pair of at least partially axially separated ring portions connected together by a web with the ring portions defining the pair of bearing races, maintaining a protective coating on said workpiece While at said preselected temperature and during said deforming step to prevent scaling and decarburization whereby said annular part is formed to close tolerances requiring minimum machining the ring portions to define the pair of bearing races while the ring portions are connected by the web, and separating the bearing races by removing the web portion.

5. In a bearing manufacturing operation in which a plurality of different sized bearings having different sized bearing races are to be manufactured from a ferrous material the method of forming pairs of bearing races from workpieces of a preselected shape comprising the steps of: deforming the workpiece into an annular part having a pair of axially separated ring portions connected together by a web with the ring portions defining the pair of bearing races, selecting the sizes of each of the ring portions to effectively utilize the material of the slug while providing combinations of bearing race sizes to best meet production requirements, machining the ring portions to define the pair of bearing races while the ring portions are connected by the web, and separating the bearing races by removing the web portion.

6. In a bearing manufacturing operation in which a plurality of different sized bearings having different sized bearing races are to be manufactured from a ferrous material the method of forming pairs of bearing races from workpieces of a preselected shape comprising the steps of: deforming the workpiece into an annular part having a pair of axially offset ring portions with the ring portions defining the pair of bearing races, selecting the sizes of each of the ring portions to effectively utilize the material of the slug while providing combinations of bearing race sizes to best meet production requirements, and machining the ring portions to define the bearing races.

7. The method of forming a cup-shaped part for subsequent formation into bearing races by deforming a slug of a ferrous bearing material comprising the steps of: deforming the slug to form a sized workpiece having a preselected shape, having the workpiece at a preselected temperature at which the strength of the material is substantially reduced from its strength at ambient temperature but below the critical temperature of the material at which air hardening occurs, deforming the workpiece While at said preselected temperature into the cup-shaped part while maintaining a web at a preselected position internally of the cup-shaped part at a preselected average thickness no less than a predetermined minimum thickness less than which the deforming forces become excessive, applying a protective coating to the workpiece while at said preselected temperature and prior to said deforming to prevent scaling and decarburization of its material at said preselected temperature whereby said cup-shaped part is formed to close tolerance requiring minimum machining, said minimum thickness being approximately /8 when said part has a diameter of around l t adjacent the web.

8. The method of forming a pair of bearing races from a ferrous material by deforming a solid slug comprising the steps of: deforming the slug to form a sized workpiece having a generally cylindrical shape, having the workpiece at a preselected temperature at which the strength of the material is substantially reduced from its strength at ambient temperature but below the critical temperature of the material at which air hardening occurs, locating the workpiece in a die having a pair of axially separated cavity portions, deforming the workpiece while at said preselected temperature in a single blow into a cup-shaped part having a pair of at least partially axially separated ring portions connected together by an intermediate web and having a bottom web being formed to a preselected average thickness no less than a predetermined minimum thickness less than which the deforming forces become excessive, applying a protective coating to the workpiece prior to said deforming to prevent scaling and decarburization at said preselected temperature and to provide S lubricity during said deforming whereby said cup-shaped part is formed to close tolerance requiring minimum machining, machining raceways in the ring portions while they are connected together, and separating the ring portions by removing the intermediate web portion.

9. The method of forming a pair of bearing races from a ferrous material by deforming a solid slug comprising the steps of deforming the slug to form a sized workpiece having a generally cylindrical shape, having the workpiece at a preselected temperature at which the strength of the material is substantially reduced from its strength at ambient temperature but below the critical temperature of the material at which air hardening occurs, locating the workpiece in a die having a pair of axially separated cavity portions, deforming the workpiece while at said preselected temperature in a single blow into a cup-shaped part having a pair of at least partially axially separated ring portions connected together by an intermediate web and having a web portion internally of the cup-shaped part, the web portion being formed to a preselected average thickness no less than a predetermined minimum thickness less than which the deforming forces become excessive, applying a protective coating to the workpiece prior to said deforming to prevent scaling and decarburization at said preselected temperature and to provide lubricity during said deforming whereby said cup-shaped part is formed to close tolerances requiring minimum machining, machining raceways in the ring portions while they are connected together, separating the ring portions by removing the intermediate web, and selecting the sizes of each of the ring portions to effectively utilize the material of the slug while providing combinations of bearing race sizes to best meet production requirements.

10. The method of forming a pair of bearing races from a ferrous material by deforming a solid slug comprising the steps of deforming the slug at ambient temperature to form a sized workpiece having a cylindrical shape, heating the workpiece to a preselected temperature in the range of about 1000 F. to about the critical temperature of the material at which air hardening occurs and below the temperature at which excessive scaling occurs, locating the workpiece in a die having a pair of axially separated cavity portions, deforming the workpiece while at said preselected temperature in a single blow into a cup-shaped part having a pair of at least partially axially separated ring portions connected together by an intermediate web and having a web portion internally of the cup-shaped part, the web portion being formed to a preselected average thickness no less than a predetermined minimum thickness less than which the deforming forces become excessive, said minimum thickness being approximately when that one of the ring portions adjacent said bottom web has an outside diameter of approximately 1% applying a protective coating to the workpiece prior to said deforming to prevent scaling and decarburization at said preselected temperature and to provide lubricity during said deforming, machining raceways in the ring portions while they are connected together, and separating the ring portions at the intermediate web portion.

11. The method of forming a pair of bearing races from a ferrous material by deforming a solid slug comprising the steps of: deforming the slug at ambient temperature to form a sized workpiece having a generally cylindrical shape, heating the workpiece to a preselected temperature in the range of about i000 F. to about the critical temperature of the material at which air hardening occurs and below the temperature at which excessive scaling occurs, locating the workpiece in a die having a pair of axially separated cavity portions, deforming the workpiece while at said preselected temperature in a single blow into a cup-shaped part having a pair of at least partially axially separated ring portions connected together by an intermediate web and having a web portion internally of the cup-shaped part, the web portion being formed to a preselected average thickness no less than a predetermined minimum thickness less than which the deforming forces become excessive, said minimum thickness being approximately 4;" when that one of the ring portions adjacent the web portion has an outside diameter of approximately 1% applying a protective coating to the workpiece prior to said deforming to prevent scaling and decarburization at said preselected temperature and to provide lubricity during said deforming, machining racetways in the ring portions while they are connected together, separating the ring portions at the intermediate Web, and selecting the sizes of each of the ring portions to effectively utilize the material of the slug While providing combinations of bearing race sizes to best meet production requirements.

12. The method of forming a pair of bearing races from a ferrous material by deforming a workpiece comprising the steps of: heating the workpiece to a preselected temperature in the range of about 1000 F. to about the critical temperature of the material at which air hardening occurs and below the temperature at which excessive scaling occurs, locating the workpiece in a die having a pair of coaxial cavity portions, deforming the workpiece While at said preselected temperature in a minimum number Olf blows into a cup-shaped part having a pair of ring port-ions having a Web intermediate to its ends whereby forming is facilitated, the Web being formed to a preselected average thickness no less than a predetermined minimum thickness less than which the deforming forces become excessive, said minimum thickness being approximately /s" when that one of the ring portions adjacent the Web has an outside diameter of approximately 1% applying a protective coating to the workpiece prior to said deforming to prevent scaling and decarburization at said preselected temperature and to provide lubricity during said deforming whereby the cupshaped part is formed to a close tolerance requiring only nominal machining in selected locations in the formation of the bearing races.

13. The method of claim 12 in which the workpiece is sheared from a solid piece of stock into a fiat plate shape having a size to pilot itself in the smaller cavity portion of the die and having a volume no greater than 110% of the enclosed volume of the die.

14. The method of claim 12 in which the workpiece is formed from a solid slug which is deformed into a cylindrical shape with a piloting cavity at one end Whereby the workpiece can be piloted upon a punch in the die and with the slug having a volume no greater than 110% of the enclosed volume of the die.

15. The method of claim 1 including maintaining on said workpiece a coating having lubricating characteristics prior to and during deforming to facilitate deformation of the workpiece.

16. The method of claim 15 with preselected temperature being in excess of about 1000 F.

17. The method of claim 16 for forming a pair of nearing races with said workpiece initially being a solid slug of mate-rial having a predetermined height and a predetermined general diameter and with said steps including deforming said workpiece while at said preselected tem- 10 perature into said intermediate part, having a generally circular shape and having a thickness substantially reduced relative to said height and having a diameter substantially greater than said predetermined general diameter.

18. The method of claim 17 with said steps including forming from said intermediate part a pair of annular bearing races with the substantially greater diameter being approximately the finished diameter of one of said bearing races.

19. The method of claim 17 with said steps including forming from said intermediate part a plurality of annular bearing race parts.

20. The method of forming a plurality of bearing races from a solid slug of ferrous material comprising the steps of: forming a workpiece having a generally cylindrical shape, heating the workpiece to a preselected temperature at least as high as about 1000 F. but substantially below the hot forming temperatures of the material at which substantial scaling and decarburization occurs, locating the workpiece in a die having axially offset cavity portions, deforming the workpiece while at said preselected temperature into a cup-shaped part having at least partially axially otfset ring portions with said ring portions defining a plurality of bearing races, and maintaining a protective coating on said workpiece while at said preselected temperature and during said deforming step to prevent scaling and decarburization whereby said cupshaped part is formed to close tolerances requiring minimum machining.

21. The method of claim 20 with said preselected temperature being below the critical temperature of the material at which air hardening occurs further including the step of maintaining on said workpiece a coating having lubricating characteristics prior to and during deforming to facilitate deformation of the workpiece.

22. The method of claim 21 with said cavity portions of said die and hence said ring portions being axially separated, and further including the step of forming a pair of bearing races from said ring portions.

23. The method of claim 20 with said cup-shaped part comprising a pair of annular, at least partially axially separated ring portions with a web located at a preselected position intermediate the ends and internally of said cupshaped part and having a preselected average thickness no less than a predetermined minimum thickness less than that at which the deforming forces become excessive.

References Cited UNITED STATES PATENTS 1,387,638 8/1921 Bingham 29-148.4 2,821,016 1/1958 Dickson 29424 2,913,811 11/1959 Benson 29148.4 1,955,195 4/1934 Lothrop et a1. 29-148.4 1,967,821 7/1934 Hess 29148.4 2,953,794 9/1960 Klooz 10-27 2,994,952 8/1961 Klooz 72-334 THOMAS H. EAGER, Primary Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION "Patent No 3 ,378 ,903 April 23 1968 Jerry E. Cardillo It is certified that error appears in the above identified patent and that said Letters Patent are hereby corrected as shown below:

Column 2, line 65, after "after" insert the Column 7,

Signed and sealed this 9th day of September 1969.

(SEAL) Attest:

line 4, after "machining" insert machining WILLIAM E. SCHUYLER, JR.

Edward M. Fletcher, Jr.

Attesting Officer Commissioner of Patents 

